Scientists alarmed as CO2 passes threshold

The amount of heat-trapping carbon dioxide in the atmosphere passed a symbolic milestone last week, reaching levels that haven’t prevailed on the Earth since long before human civilization began.

The long-expected announcement Friday by the National Oceanic and Atmospheric Administration — that CO2 concentrations had finally hit 400 parts per million at a key measuring station in Hawaii — means little by itself. But it’s a sign that time is slipping away to head off or lessen the rising sea levels, worsening storms, species die-offs and other fallout from global warming, scientists and climate activists warned.

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Still, there are few signs that Washington will emerge from its deep snooze on the issue.

Congress remains unable to pass serious legislation to tackle climate change. Efforts to reach a major binding international climate change treaty have sputtered. And while the Obama administration has made some strides in lowering greenhouse gas emissions, including increasing fuel-efficiency standards for cars, climate experts say much more needs to be done — and fast.

“We’ve never been here before, certainly not while human beings were on the planet,” Melanie Fitzpatrick, climate scientist at the Union of Concerned Scientists, said, estimating that it’s been 3 million to 5 million years since the planet has had such high carbon dioxide levels.

“The carbon dioxide concentration in the atmosphere is like the thermostat in your house. Every time you turn it up, we are essentially turning up the heat in the planet,” said Jon Hoekstra, chief scientist at the World Wildlife Fund. “We’re essentially baking ourselves in, perhaps quite literally.”

NOAA said the daily mean CO2 concentration was 400.03 ppm on Thursday at Mauna Loa, Hawaii, the world’s oldest continuous carbon dioxide measurement station. That was the first time the figure had crossed 400 ppm there since measurements began at the site in 1958, the agency said.

NOAA said last year that sites in the Arctic had already reached 400 ppm, but measurements from the facility in Hawaii are closely watched as an indicator of broader trends on the planet.

“It’s unprecedented,” said James Butler, director of the Global Monitoring Division of NOAA’s Earth System Research Laboratory. “Hitting 400 is just saying, ‘Folks, we haven’t addressed this yet.’”

Butler said the planet hasn’t seen atmospheric levels of carbon dioxide this high since the Pliocene era, between 5 million and 2.5 million years ago. He said the global average temperature will probably reach 400 ppm in one or two years.

Scientists warn that continued increases could result in catastrophe. A federal report released earlier this year, for example, said 5 million Americans living in low-lying areas could be affected by sea-level rise in the coming decades.

And global emissions appear poised to continue soaring. Not only has the CO2 concentration risen over the decades, NOAA said, but the rate of increase has been accelerating — “from about 0.7 ppm per year in the late 1950s to 2.1 ppm per year during the last 10 years.”

“Before the Industrial Revolution in the 19th century, global average CO2 was about 280 ppm,”